Dual fuel vehicles generally include a fuel system having an internal combustion engine that can run on either gas or diesel fuel. Such fuel systems have an injector to pump both fuels to the engine from a gas supply and a diesel supply. However, gas pressure is required to be regulated relative to diesel pressure in order to properly maintain and run the engine. A regulator is used to control such relative pressures.
Dome loaded regulators are well known in the art and generally include a dome space, a gas flow path having an inlet and outlet, a spring-biased seat, and a diaphragm. When gas pressure decreases from a desired pressure, compared to the diesel pressure, the diaphragm moves away from the dome space and toward the spring-biased seat. This movement widens the gas flow path between the inlet and the outlet, thereby increasing the flow rate and corresponding pressure. After the gas pressure is restored to a normal pressure, compared to the diesel pressure, the bias of the diaphragm causes it to move back to its original position. When the gas pressure increases from the desired pressure, the diaphragm moves away from the spring-biased seat and thus decreases the gas flow rate. This restores a normal pressure of gas in the regulator, compared to the diesel pressure, and also returns the diaphragm to its original position. An exemplary regulator is described in U.S. Pat. No. 8,167,001 that issued to Larsen on May 1, 2012 (the '001 patent).
Although traditional regulators, including the regulator described in the '001 patent, may adequately control the relative pressures of diesel and gas in a normal mode, they may not function properly during a failure condition. Specifically, when a gas fuel leak occurs in the fuel system of the '001 patent and the gas pressure falls, the traditional regulator may widen the gas flow path and feed more gas fuel into the leak. Similarly, if all the gas fuel in the fuel system has been exhausted, the traditional regulator will again widen the gas flow path, even though no more gas fuel is available to be pumped to the engine.
The disclosed pressure regulator is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.